An implant material for replacing hard tissue containing as essential components A) 30 to 95% by weight of a thermotropically mesomorphic polymer, B) 5 to 70% by weight of an apatite and C) 0 to 60% by weight of a fibrous or particulate filler which differs from B)....http://www.google.ca/patents/US5092890?utm_source=gb-gplus-sharePatent US5092890 - Implant materials for hard tissue

The present invention relates to an implant material for replacing hard tissue in the body, containing as essential components

A) 30 to 95% by weight of a thermotropically mesomorphic polymer,

B) 5 to 70% by weight of an apatite and

C) 0 to 60% by weight of fibrous or particulate fillers which differ from B), or mixtures thereof.

Surgical or orthopedic treatments which result in a loss of pieces of bone or of joints frequently have to be followed by prosthetic operations in order to replace the pieces which have been removed.

The main constituents of bone in human and animal bodies are collagen (organic material) and apatite (inorganic material).

Implant materials which have hitherto been employed to replace hard tissue are natural materials, metallic or ceramic materials and--recently--systems based on reinforced thermoplastic polymers.

Although natural materials such as ivory or animal bone are often satisfactorily compatible with the tissue into which they are implanted, nevertheless their mechanical properties are difficult to predict and poorly reproducible.

The compatibility of metallic, ceramic or polymeric materials with biological materials is often low, which may result in inflammations and infections on insertion of the prosthesis in particular.

Also known are implant materials composed of a combination of metallic or ceramic materials and polymers, the latter being intended, in particular, to seal the material surface, which leads to a low coefficient of friction. The fixing to the bone is often brought about by in situ polymerization which, because of the local heating which occurs during this, may lead to serious inflammations and tissue damage.

Because, as already mentioned, bone essentially consists of collagen and apatite, there has been no lack of attempts to develop implant materials which contain these materials.

Sintered apatites have attracted interest as replacements for bone and teeth, because of their compatibility with biological tissue, but the great brittleness and the inadequate mechanical strength hinder their wide use (cf. H. Aoki et al., Ceramics 10 (1975) 57-66).

DE-A 2,821,354 decribes composite implant materials comprising a ceramic body as continuous phase with perforations filled with synthetic resin, and, although these have certain advantages over sintered apatites with regard to mechanical properties, they are not yet completely satisfactory. In addition, the process of manufacture of products which contain sintered apatite is relatively costly.

WO 82/01310 describes a composite material which consists of a homo- or copolyolefin with a weight average molecular weight of more than 20,000 and up to 80% by weight of a particulate inorganic filler. The preferred example mentioned for the inorganic filler is natural or synthetic hydroxyapatite.

Although materials of this type have satisfactorily reproducible mechanical properties, nevertheless their strength and rigidity, in particular, still require improvement.

DE-A 3,542,535 also relates to implant materials for replacing hard tissue in the live body. These consist of 10 to 90% by weight of glass fibers which consist predominantly of calcium phosphate, and 10 to 90% by weight of organic polymers, particularly preferred being polyethylene, polypropylene, poly(methyl methacrylate) and poly(trifluoroethyl methacrylate); the two latter polymers are said to result in particularly high strengths, but these are still not yet completely satisfactory.

Hence the object of the present invention was to make available implant materials for replacing hard tissue in the body, which are satisfactorily compatible with biological tissue and whose mechanical properties are satisfactorily reproducible. It was particularly intended to improve the rigidity and strength by comparison with known polymer-based materials.

This object is achieved according to the invention by the implant materials defined in the introduction.

The implant materials according to the invention contain as component A) 30 to 95, preferably 35 to 90, and in particular 40 to 75, % by weight of a thermotropically mesomorphic polymer. The latter have been described in recent years in a large number of publications and patent applications.

Thermotropically mesomorphic polymers have an anisotropic melt phase which is easy to detect using the polarizing microscope method described in U.S. Pat. No. 4,118,372. Between crossed polarizers, the polymer melts, which are applied in a layer thickness of 10 μm between glass plates, have textures which can be assigned to a mesomorphic phase.

To achieve an anisotropic (liquid crystalline) melt phase it is usually necessary for the main chain to have a certain degree of linearity which can be achieved by appropriate choice of the ratios of monomer amounts. The anisotropy of the melt phase, and the orientation of the polymer molecules associated therewith, result in very high strengths and rigidities in shaped articles produced from polymers of this type.

It should be emphasized that, in principle, all thermotropically mesomorphic polymers, irrespective of the composition, are suitable as component A) for producing the implant materials according to the invention.

It is possible to say in general that thermotropically mesomorphic polymers contain units which are derived from

a1) aromatic or aliphatic dicarboxylic acids,

a2) aromatic or aliphatic diols, diamines or corresponding monomers with an amino and a hydroxyl group,

The composition of these products can vary within wide limits, and a large number of monomers can be employed. It is essential that the polymers have thermotropically mesomorphic properties, which can easily be checked by the method which has already been mentioned and is described in U.S. Pat. No. 4,118,372.

Not all combinations of monomers a1) to a4) in any desired molar ratio result in thermotropically mesomorphic polymers, and it is scarcely possible to make a general statement about suitable ratios of amounts.

However, the relevant literature and a large number of patent applications describe suitable thermotropically mesomorphic systems which will now be illustrated in detail below, firstly by a list of suitable examples of monomers and corresponding polymers. Monomers a1 : Terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4,'-dicarboxydiphenyl, 4,4"-dicarboxyterphenyl, dicarboxydiphenyl derivatives of the general formulae I and II

Likewise suitable are p,p'-, m,m'-, and p,m'- dicarboxydiphenyl carbonates of the general formulae VI to VIII ##STR5##

The abovementioned carboxylic acids can also have substituents such as C` -C4 -alkyl, C1 -C4 -alkoxy or halogen. Finally, mention should also be made of some aliphatic dicarboxylic acids such as cis- and trans-1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid as well as the appropriately substituted derivatives thereof.

Further suitable monomers from groups a1) to a4) are listed, for example, in EP-A 206,600.

A number of preferred thermotropically mesomorphic polymers are presented hereinafter.

1. Thermotropically mesomorphic polyesters composed of

1a) 10 to 25 mol-% of repeating units of the formula ##STR6## 3,3',5,5'-tetramethyl-4,4,'-dihydroxydiphenyl is advantageously used as starting material;

1b) 5 to 15 mol-% of repeating units of the formula ##STR7## hydroquinone is used as preferred starting material;

1c) 5 to 15 mol-% of repeating units of the formula ##STR8## 4,4'-dihydroxydi-phenyl is used, for example, as starting compound;

1d) at least 10 mol-% of repeating units of the formula ##STR9## 4-hydroxybenzoic acid is used as preferred starting compound;

1e) a molar amount which is equivalent to the total of 1a), 1b) and 1c) of repeating units of the formula ##STR10## terephthalic acid is used, for example, as suitable starting compound.

In preferred completely aromatic polyesters of this type, some of the units b) and/or c) are replaced by

1f) repeating units of the formula ##STR11## a suitable starting material for this is, for example, tert.-butylhydroquinone and/or

1g) repeating units of the formula ##STR12## phenylhydroquinone is used as preferred starting compound.

Completely aromatic polyesters of this type advantageously contain the repeating units 1f) and/or 1g) in an amount of from 2 to 20 mol-%. It has furthermore proved advantageous for the total of the molar proportions of units 1a) and 1f) and/or 1g) to be from 20 to 40 mol-%.

In other preferred completely aromatic polyesters, some of the units 1b) and/or 1c) are replaced by 1h) repeating units of the formula ##STR13##

1i) repeating units of the formula ##STR14##

1j) repeating units of the formula ##STR15## and/or

1k) repeating units of the formula ##STR16## Used as starting material for component 1h) is 2,6-dihydroxyanthraquinone, for component 1i) is 2,7-dihydroxynaphthalene, for component 1j) is 2,6-dihydroxynaphthalene and for component 1k) is 4,4,'-di(p-hydroxyphenoxy)diphenyl sulfone.

It has proven appropriate for the total of the molar proportions of the units 1a), 2h), 1i), 1j) and 1k) in the polyesters according to the invention to be from 20 to 40 mol-%.

It is advantageous to use in each case the amount of terephthalic acid equivalent to the total of the dihydroxy compounds.

Polyesters of this type are described in EP-A 226,839.

2. Thermotropically mesomorphic polyesters composed of 2a) 5 to 35 mol-% of repeating units of the formula ##STR17## t-butylhydroquinone is used as starting compound;

2b) 3 to 15 mol-% of repeating units of the formula ##STR18## 4,4,'-dihydroxybiphenyl is used as starting compound;

2c) a molar amount equivalent to the total of 2a) and 2b) of repeating units of the formula ##STR19## terephthalic acid is used as starting compound;

2d) at least 10 mol-% of repeating units of the formula ##STR20## p-hydroxybenzoic acid is used as starting compound.

In preferred polyesters of this type, some of the units b) are replaced by 2e) repeating units of the formula ##STR21## (a suitable starting compound is hydroquinone) and/or

2h) repeating units of the formula ##STR24## 2,6-dihydroxyna-phthalene is used as suitable starting compound.

Polyesters of this type contain the units 2e), 2f) and/or 2g) in an amount of from 5 to 12 mol-%. It has furthermore proven advantageous for the molar proportion of units 2a) to be from 15 to 25 mol-%. In particularly advantageous polyesters the molar proportion of the total of 2a) and one or more units 2e), 2f) and 2g) is from 25 to 35 mol-%.

It has proven advantageous for some of the units 2c to be replaced by units of the formula ##STR25## Isophthalic acid is used as suitable starting compound.

It is obvious that it is advantageous in each case to use the amount of terephthalic acid and/or isophthalic acid which is equivalent to the total of the hydroxy compounds.

Polyesters of type 2 are described in EP-A 226,078.

3. Thermotropically mesomorphic polyether esters composed of

3a) at least 10 mol-% of repeating units of the formula ##STR26## p-hydroxybenzoic acid is used, for example, as starting material,

3b) a molar amount equivalent to the total of c) and d) of repeating units of the formula ##STR27## where terephthalic acid is used as preferred starting compound,

3c) 5 to 20 mol-% of repeating units of the formula ##STR28## 4,4,'-di(p-hydroxyphenoxy)diphenyl sulfone is used, for example, as starting compound, and

3d) 10 to 30 mol-% of repeating units of the formula ##STR29## tert.-butylhydroquinone is advantageously used as starting compound.

Preferred polyether esters of this type contain, besides component 3a), 10 to 15 mol-% of component 3c), 15 to 25 mol-% of component 3d) and a molar amount equivalent to the total of 3c) and 3d) of component 3b).

Some of the units 3d) can be replaced by

3e) repeating units of the formula ##STR30## hydroquinone is used, for example, as starting compound, and/or

3f) repeating units of the formula ##STR31## 4,4,'-dihydroxydiphenyl is preferably used as a suitable starting compound, and/or

3g) repeating units of the formula ##STR32## where R is methyl, phenyl or chlorine, and n is 1, 2 or 3.

It is advantageous for completely aromatic polyether esters of this type to contain the repeating units 3e) and/or 3f) in an amount of from 5 to 10 mol-%. In another preferred composition, the completely aromatic polyether esters contain the component 3g) in an amount of from 5 to 20 mol-%.

The content of repeating units 4f) is advantageously from 2 to 10 mol-%.

It has furthermore proven advantageous for the molar proportion of the total of components 4b) and 4d) in the polyester carbamides to be from 15 to 20 mol-%.

In other polyester carbamides some of the component 4c) is replaced by at least one of the repeating units of the formulae ##STR39##

Suitable starting compounds for the repeating units of these formulae are 2,6-dihydroxyanthraquinone, 2,6-dihydroxynaphthalene and 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl. The proportion of the repeating units of these formulae advantageously totals from 2 to 10 mol-%.

Products of this type are described in EP-A 230,551.

5. Polyesters composed of 5a) at least 10 mol-% of repeating units of the formula ##STR40## where 4-hydroxybenzoic acid is used as starting compound; 5b) a molar amount equivalent to the total of components 5c) and 5d) of repeating units of the formula ##STR41## terephthalic acid is advantageously used as starting compound;

5c) 3 to 20 mol-% of repeating units of the formulae ##STR42## hydroquinone is used, for example, as starting compound; ##STR43## 4,4'-dihydroxybiphenyl is used, for example, as starting compound;

5d) 5 to 30 mol-% of repeating units of the formula ##STR44## where 4,4'-di(p-hydroxyphenoxy)diphenyl sulfone is advantageously used as starting compound.

Preferred polyether esters are composed of at least 20 mol-%, advantageously up to 50 mol-%, of component 5a), 10 to 25 mol-% of component 5d), 5 to 15 mol-% of component 5c) and a molar amount equivalent to the total of 5c) and 5d) of component 5b). The polyether esters advantageously contain as component 5c) from 5 to 15 mol-% of repeating units which are derived from hydroquinone or a mixture of hydroquinone and dihydroxydiphenyl.

Polyether esters of the abovementioned type are described in EP-A 226,847.

6. Polyester amides composed of

6a) 5 to 35 mol-% of repeating units of the formula ##STR45##

6b) 5 to 15 mol-% of repeating units of the formula ##STR46##

6c) a molar amount equivalent to the total of components 6a) and 6b) and, where appropriate, 6e) of repeating units of the formula ##STR47##

6d) at least 10 mol-% of repeating units of the formula ##STR48##

6e) 2 to 15 mol-% of repeating units of the formulae ##STR49## where some of the repeating units of the last formula can be replaced by repeating units of the formula ##STR50## with the proviso that the total of the molar proportions of components 6a), 6b), 6c), 6d) and 6e) is 100 mol-% in each case.

The repeating units 6a) to 6e) are preferably derived from the following starting compounds:

6a) t-butylhydroquinone

6b) 4,4'-dihydroxydiphenyl

6c) terephthalic acid

6d) p-hydroxybenzoic acid

6e) p-aminobenzoic acid, p-aminophenol and 1,4-diaminobenzene.

Polyester amides with these structural units are described in EP-A 230,545.

7. Polyester amides composed of

7a) 3 to 30 mol-% of repeating units of the formula ##STR51##

7b) 3 to 30 mol-% of repeating units of the formulae ##STR52##

7c) 2 to 25 mol-% of at least one of the repeating units of the formulae ##STR53##

7d) a molar amount equivalent to the total of components 7a), 7b) and 7c), except the second repeating units of the formula 7b), of repeating units of the formula ##STR54## where some of these repeating units can be replaced by those of the formula ##STR55##

7e) where appropriate 5 to 25 mol-% of repeating units of the formula ##STR56##

7f) repeating units of the formula ##STR57## where the molar proportions of components 7a) to 7f) total 100 mol-% in each case.

The units 7a) to 7f) are preferably derived from

7a): t-butylhydroquinone

7b): m-aminophenol or m-aminobenzoic acid,

7c): hydroquinone, 4,4'-dihydroxydiphenyl or resorcinol,

7d): terephthalic acid or isophthalic acid

7e): m-hydroxybenzoic acid and

7f): p-hydroxybenzoic acid.

Preferred polyester amides contain 5 to 20 mol-% of repeating units 7a), 5 to 20 mol-% of repeating units of the formula 7b), which are derived from m-aminophenol, and 5 to 20 mol-% of the formula 7c), in particular those units 7c) which are derived from hydroquinone, as well as the appropriate amount of repeating units of the formulae 7d) and, in addition, repeating units 7f).

Other preferred polyester amides contain 5 to 20 mol-% of units 7a), 5 to 20 mol-% of units 7b) which are derived from m-aminobenzoic acid, as well as 5 to 20 mol-% of repeating units 7c) which are derived from hydroquinone and 4,4'-dihydroxydiphenyl, as well as the appropriate amount of repeating units of the formulae 7d) and, in addition, repeating units 7f).

Further preferred polyester amides contain 5 to 20 mol-% of units 7a), 5 to 20 mol-% of units 7b) which are derived from m-aminobenzoic acid, and 5 to 20 mol-% of units 7c) which are derived from hydroquinone, as well as the appropriate amount of repeating units of the formulae 7d) and, in addition, repeating units 7f).

Polyester amides of type 7 are described in EP-A 230,546.

8. Polyester amides composed of

8a) 3 to 30 mol-%, in particular 5 to 25 mol-%, of repeating units of the formula ##STR58## m-aminophenol is a suitable starting compound;

8b) 3 to 25 mol-%, preferably 5 to 20 mol-%, of at least one of the repeating units of the formulae ##STR59## examples of suitable starting compounds are hydroquinone, 4,4'-dihydroxybiphenyl and resorcinol. Particularly preferred repeating units are derived from hydroquinone or 4,4'-dihydroxydiphenyl or mixtures thereof, 8c) a molar amount equivalent to the total of components

8a) and 8b) of repeating units of the formulae ##STR60## examples of suitable starting compounds are terephthalic acid and isophthalic acid,

8d) repeating units derived from p-hydroxybenzoic acid, advantageously in an amount of at least 10 mol-%, in particular at least 20 mol-%;

8e) where appropriate from 5 to 25 mol-%, in particular 5 to 15 mol-%, of repeating units of the formula ##STR61## an example of a suitable starting compound is m-hydroxybenzoic acid.

Polyester amides with these units are described in EP-A 226,080.

9. Polyester imides composed of

9a) 5 to 35 mol-%, in particular 7 to 31 mol-%, of repeating units of the formulae ##STR62## X and n can each vary. X is --O--, --S--, --SO2 --, --CO--, --CH2 -- or C(CH3)2 --, in particular --O--, --SO2 -- or --CH2 --, and n is 0 or 1, in particular 1; examples of suitable starting compounds are

4,4'-di(4-carboxy-N-phthalimido)diphenyl ether,

4,4'-di(4-carboxy-N-phthalimido)diphenylmethane,

4,4'-di(4-carboxy-N-phthalimido)diphenyl sulfone,

4,4'-di(4-carboxy-N-phthalimido)diphenyl sulfide,

4,4'-di(4-carboxy-N-phthalimido)diphenyl ketone,

3,4'- or 3,3'-di(4-carboxy-N-phthalimido)diphenyl ether,

3,4'- or 3,3'-di(4-carboxy-N-phthalimido)diphenyl sulfide,

3,4'- or 3,3'-di(4-carboxy-N-phthalimido)diphenyl sulfone,

3,4'- or 3,3'-di(4-carboxy-N-phthalimido)diphenyl ketone,

3,4'- or 3,3'-di(4-carboxy-N-phthalimido)diphenylmethane;

(processes for the preparation of such compounds are described in Polymer Science (A-1), Vol. 7, pages 320-332);

9b) 0 to 30 mol-%, in particular 0 to 20 mol-%, of repeating units of the formulae ##STR63## suitable starting compounds for these units are terephthalic acid and isophthalic acid;

9c) a molar amount equivalent to the total of components

9a) and 9b) of at least one of the repeating units of the following formulae ##STR64## examples of suitable starting compounds are hydroquinone, resorcinol, 4,4'-dihydroxybiphenyl and 2,7-dihydroxynaphthalene;

9d) at least 10 mol-%, in particular at least 20 mol-%, of repeating units of the formula ##STR65## an example of a suitable starting compound is p-hydroxybenzoic acid;

9e) where appropriate 5 to 25, in particular 10 to 20, mol-% of repeating units of the formula ##STR66## an example of a suitable starting compound is m-hydroxybenzoic acid.

Preferred polyester imides contain as component 9c) 10 to 31 mol-% of repeating units which are derived from hydroquinone, and/or 5 to 25 mol-% of repeating units which are derived from the other starting compounds listed under 9c). Particularly preferred components 9c) are repeating units derived from hydroquinone, resorcinol and/or 4,4'-dihydroxydiphenyl and mixtures thereof.

Polyester imides of the abovementioned type are described in EP-A 227,947.

10. Polyester amide imides composed of

10a) 5 to 35 mol-%, in particular 7 to 25 mol-%, of repeating units of the formulae ##STR67## where suitable starting compounds are the same as those mentioned above for units 9a) of the polyester imides 9); compounds of the formula I and II can be obtained, for example, as described in Polym. Sci. (A-1), 7 (1969) 320-332

10b) 0 to 30 mol-%, in particular 0 to 20 mol-%, of repeating units of the formulae ##STR68## where examples of suitable starting compounds are terephthalic acid and isophthalic acid;

10c) a molar amount equivalent to the total of components 10a) and 10b) of at least one of the repeating units of the following formulae ##STR69## where starting compounds which may be mentioned are p-aminophenol, m-aminophenol, hydroquinone, resorcinol and 4,4'-dihydroxydiphenyl;

10d) where appropriate 5 to 25 mol-%, in particular 5 to 20 mol-%, of at least one of the repeating units of the formulae ##STR70## where suitable starting compounds are m-hydroxybenzoic acid, p-aminobenzoic acid and m-aminobenzoic acid;

10e) repeating units, in particular in an amount of at least 10 mol-%, of the formula ##STR71## where p-hydroxybenzoic acid may be mentioned as a suitable starting compound.

It is obvious that the total of the molar percentages of components 10a) to 10e) is 100 mol-% in each case.

The polyester amide imides according to the invention advantageously contain as component 10c) 5 to 20 mol-% of repeating units derived from m-aminophenol, and/or 2 to 8 mol-% of repeating units derived from p-aminophenol and/or 5 to 20 mol-% of at least one of the repeating units derived from hydroquinone, resorcinol and 4,4'-dihydroxydiphenyl.

11a) 5 to 35 mol-%, in particular 7 to 25 mol-%, of repeating units of the formulae ##STR72## where X may vary and is, in each case, --O--, --S--, --SO2 --, --CO--, --CH2 or --C(CH3)2 --, and n is 0 or 1;

suitable starting compounds are listed for units

9a) for polymers of type 9;

the preparation of starting compounds of this type is described, for example, in J. Polym. Sci. (A-1), 7 (1969) 321-332;

11b) 0 to 30 mol-%, in particular 0 to 20 mol-%, of repeating units of the formulae ##STR73## where terephthalic acid and isophthalic acid may be mentioned as starting compounds;

11c) a molar amount equivalent to the total of components 11a) and 11b) of aromatic dihydroxy compounds, namely 3 to 35 mol-% of repeating units of the formula ##STR74## where tert.-butylhydroquinone can be used as suitable starting compound, as well as at least one of the following repeating units in an amount of from 2 to 25 mol-% ##STR75## where hydroquinone and 4,4'-dihydroxydiphenyl may be mentioned as starting compounds, as well as 0 to 25 mol-% of repeating units of the formula ##STR76## where resorcinol may be mentioned as suitable starting compound;

11d) where appropriate 5 to 25 mol-%, in particular 5 to 20 mol-%, of repeating units of the formula ##STR77## an example of a suitable starting compound is m-hydroxybenzoic acid;

11e) repeating units of the following formula, advantageously in an amount of not less than 10 mol-% ##STR78## where p-hydroxybenzoic acid can be employed as starting compound.

It is obvious that the total of the molar proportions of components 11a), 11b), 11c), 11d) and 11e) is 100 mol-% in each case.

Advantageous polyester imides contain as components 11c) 5 to 25 mol-% of repeating units derived from t-butylhydroquinone, and 5 to 20 mol-% of at least one of the repeating units derived from hydroquinone, resorcinol or 4,4'-dihydroxydiphenyl.

Further preferred sorts of polyester imides of type 11 are described in EP-A 225,537.

12. Polyester amide imides composed of 12a) 5 to 35 mol-% of repeating units of the formula ##STR79## where X and n have the meanings described above for units 9a) in polymers 9;

12c) a molar amount equivalent to the total of components 12a) and 12b) of at least one of the following repeating units

12c1) 3 to 35 mol-% of units of the formula ##STR80##

12c2) 0 to 10 mol-% of units of the formula ##STR81##

12c3) 2 to 25 mol-% of units of the formula ##STR82##

12c4) 2 to 20 mol-% of units of the formula ##STR83##

12c5) 0 to 20 mol-% of units of the formula ##STR84## and

12c6) 2 to 20 mol-% of units of the formula ##STR85## where suitable starting compounds are t-butylhydroquinone, p-aminophenol, m-aminophenol, hydroquinone, resorcinol and 4,4'-dihydroxydiphenyl;

12d) at least 10 mol-% of repeating units of the formula ##STR86## where a starting compound which may be mentioned is p-hydroxybenzoic acid; and

12e) 0 to 25 mol-% of at least one of the repeating units of the formula ##STR87## where these units are derived from m-hydroxybenzoic acid, p-aminobenzoic acid and m-aminobenzoic acid.

Polyester amide imides of type 12 are described in EP-A 225,529.

13. Polyether ester imides composed of

13a) 5 to 35 mol-% of repeating units of the formula ##STR88## where 4,4'-di(p-hydroxyphenoxy)diphenyl sulfone may be mentioned as suitable starting compound;

13b) 5 to 35 mol-% of repeating units of the formulae ##STR89## where X is a chemical bond, --O--, --S--, --SO2 --, --CO--, --CH2 -- or ═C(CH3)2 and n is 0 or 1; suitable starting compounds are listed under units 9a) in polymers of type 9;

14c) 0 to 20 mol-%, in particular 2 to 18 mol-%, of at least one of the repeating units of the formulae ##STR91## where 4,4'-dihydroxy-diphenyl, hydroquinone and 3,3',5,5'-tetramethyl-4,4'-dihydroxydiphenyl may be mentioned as starting compounds,

14d) 0 to 20 mol-%, advantageously 2 to 15 mol-%, of at least one of the repeating units of the following formulae ##STR92## where 2,7-dihydroxynaphthalene, resorcinol, m-aminophenol and m-phenylenediamine may be mentioned as starting compounds,

14e) a molar amount equivalent to the total of components 14b), 14c) and 14d) of repeating units derived from terephthalic acid, where the total of molar percentages of components 14a), 14b), 14c), 14d) and 14e) is 100 mol-% in each case

It is also possible for a portion, eg. up to 50% of the required molar amount, of the units derived from terephthalic acid to be replaced by repeating units derived from isophthalic acid.

It is furthermore possible for a portion of components 14a), eg. up to an amount of 15 mol-%, to be replaced by at least one of the repeating units of the following formulae ##STR93## Suitable starting compounds are p-aminobenzoic acid, m-hydroxybenzoic acid and m-aminobenzoic acid.

Products of this type are described in EP-A 230,550.

15. Liquid-crystalline polycondensates which contain carbamide groups and are composed of

15a) aromatic hydroxy and/or amino carboxylic acids in which the hydroxyl or amino group is not vicinal to the carboxyl group

15b) 0.1 to 20 mol-% of urea 15c) aromatic dihydroxy, diamino and/or hydroxy amino compounds in which the hydroxyl and amino groups are not vicinal to one another

15d) a molar amount equivalent to the total of components b and c of aromatic dicarboxylic acids in which the carboxyl groups are not vicinal.

Preferred polymers of this type contain 15a) at leasts 10 mol-% of at least one of the repeating units ##STR94## where R1 and R2 can be identical or different and each is 1,4-phenylene, 1,3-phenylene, 2,7-naphthylene or 2,6-naphthylene

15b) 0.1 to 20 mol-% of repeating units of the formula ##STR95##

15c) at least one of the repeating units of the formula

--X--R3 --Y--

where R3 is 1,4-phenylene, 1,3-phenylene, 2,6-naphthylene, 2,7-naphthylene, 4,4'-biphenylylene, 3,4'-biphenylylene, 2,6-anthraquinonylene, it being possible for the radicals to be substituted by halogens, alkyls of up to 4 carbons or a phenyl, and R3 is also ##STR96## and X and Y can be identical or different and each is oxygen or --NH--,

15d) an amount equivalent to the total of components 15b) and 15c) of repeating units of the formula ##STR97## where R4 is 1,4-phenylene, 1,3-phenylene or the following ##STR98## where Z is --O--, --S--, --SO2 --, --CO--, --CH2 --, =C(CH3)2 in each case, and n is 0 or 1, or R4 is also ##STR99##

16d) at least 10 mol-% of repeating units of the formula ##STR103## where the total of the molar proportions of components 16a), 16b), 16c) and 16d) is 100 mol-% in each case and the molar ratio of components 16a) and 16b) to component 16c) is in the range from 0.9:1 to 1.1:1.

Starting compounds which may be mentioned for the various units are t-butylhydroquinone, resorcinol, terephthalic acid and p-hydroxybenzoic acid.

17. Thermotropically mesomorphic polyesters composed of

17a) at least 10 mol-% of units derived from p-hydroxybenzoic acid,

17b) 1 to 25 mol-% of repeating units of the formula ##STR104## 17c) 5 to 20 mol-% of at least one of the repeating units of the following formulae ##STR105##

17d) 5 to 15 mol-% of repeating units of the formula ##STR106##

17e) 10 to 60 mol-% of repeating units of the formula ##STR107## where the total of the molar proportions of 17a), 17b), 17c) and 17e) is 100 mol-% in each case and the molar ratio of components 17b)+17c)+17d) to component 17e) is in the range from 0.9:1 to 1.1:1.

Preferred starting material are as follows for repeating units of the formula

where the molar ratio of b1 to b2 is in the range from 1.04:1 to 19:1, preferably from 1.5:1 to 10:1, and 18c) 20 to 35 mol-% of a mixture of

18c1) hydroquinone

18c2) 4,4'-dihydroxydiphenyl and

18c3) 0 to 5 mol-% of a dihydroxy compound of the general formula ##STR108## where R and R' are alkyls of up to 4 carbons, halogen or an aryl, n and p are 1, 2 or 3, and m is 0 or 1, the molar ratio of 18c1) to 18c2) is in the range from 0.1:1 to 2.67:1, preferably from 0.5:1 to 2.33:1, and the molar ratio of 18b) to 18c) is in the range from 0.9:1 to 1.1:1, preferably from 0.98:1 to 1.02:1.

where the molar ratio of 19b1) to 19b2) is in the range from 1.04:1 to 19:1, preferably from 1.5:1 to 10:1, and 19c) 20 to 35 mol-% of a mixture of

19c1) hydroquinone

19c2) 4,4'-dihydroxydiphenyl and

19c3) 0.5 to 5 mol-% of

19c31) 2,7-dihydroxynaphthalene and/or

19c32) 1,3-dihydroxybenzene and/or

19c33) an aromatic dihydroxy compound of the general formula ##STR109## where X is --CH2 --, --C(CH3)2 --, --S--, --SO2 --, --O-- or --CO--, or the derivatives thereof substituted in the nucleus by chlorine, bromine, aryl or C1 -C8 -alkyl or alkoxy, and/or

19c34) a compound of the general formula ##STR110## where X is --NH2 or --OH and the substituents are meta or para with respect to one another, or the derivatives thereof which are substituted in the nucleus by chlorine, bromine, aryl or C1 -C8 -alkyl or alkoxy, where the molar ratio of 19c1) to 19c2) is in the range from 0.1:1 to 2.67:1, preferably from 0.5:1 to 2.33:1, and the molar ratio of 19b) to 19c) in the range from 0.9:1 to 1.1:1, preferably from 0.98:1 to 1.02:1.

where the molar ratio of 20a1) to 20a2) is in the range from 5:1 to 41:1, preferably from 6:1 to 20:1,

20b) 20 to 37.5 mol-% of a mixture of

20b1) terephthalic acid and

20b2) isophthalic acid

where the molar ratio of 20b1) to 20b2) is in the range from 1.04:1 to 19:1, preferably from 1.5:1 to 10:1, and

20c) 20 to 37.5 mol-% of a mixture of

20c1) hydroquinone

20c2) 4,4'-dihydroxyiiphenyl

where the molar ratio of 20c1) to 20c2) is in the range from 0.1:1 to 2.67:1, preferably from 0 5:1 to 2.33:1, and the molar ratio of 20b) to 20c) is in the range from 0.9:1 to 1.1:1, preferably from 0.98:1 to 1.02:1.

21b3) 0.5 to 5 mol-% of a dicarboxylic acid of the general formula ##STR111## where X is --O--, --S--, --SO2 --, --CO--, --CH2 -- or --C(CH3)2 --, n is 0 or 1, and the two imide nitrogens are meta or para to X, or the derivatives thereof substituted in the nucleus by C1 -C8 -alkyl, C1 -C8 -alkoxy, aryl, chlorine or bromine and

where the molar ratio of 21b1) to 21b2) is in the range from 1.04:1 to 19:1, preferably from 1 5:1 to 10:1, and

21c) 20 to 35 mol-% of a mixture of

21c1) hydroquinone

21c2) 4,4'-dihydroxydiphenyl

where the molar ratio of 21c1) to 21c2) is in the range from 0.1:1 to 2.67:1, preferably from 0.5:1 to 2.33:1, and the molar ratio of 21b) to 21c) is in the range from 0.9:1 to 1.1:1, preferably from 0.98:1 to 1.02:1.

Suitable starting compounds 21b3) which may be mentioned are the compounds listed under the unit 9a) for the polymers of type 9 described above.

It is obvious that the total of components 26b) and 26c) is equimolar to the amount of component 26d).

It is also possible for components 26a), 26b) and 26c) to be substituted by one or more alkyl or alkoxy of up to 4 carbons, halogen, phenyl or combinations thereof. 27. Thermotropically mesomorphic polyesters composed of

28b) 5 to 45 mol-%, in particular 10 to 40 mol-%, of repeating units of the formula

--O--R'--O--

where R' is a divalent radical having at least one phenyl ring (a suitable starting compound is hydroquinone), and

28c) 5 to 45 mol-%, in particular 10 to 40 mol-%, of repeating units of the formula ##STR125## where R2 is a divalent radical having at least one phenyl ring (a preferred starting compound is terephthalic acid).

Other preferred polyesters contain 60 to 80 mol-% of units 28a), 10 to 20 mol-% of 28b) and 10 to 20 mol-% of units 28c). It is obvious that the repeating units can also be substituted by one or more alkyl or alkoxy of up to 4 carbons, halogen, phenyl or combinations thereof.

29b) 5 to 45 mol-% of repeating units of the formula ##STR127## where R' is a divalent radical consisting of at least one phenyl ring or is a divalent trans-cyclohexane ring (a preferred starting compound is terephthalic acid),

29c) 5 to 45 mol-% of repeating units of the formula

--Y--R2 --Z--

where R2 is a divalent radical consisting of at least one phenyl ring, Y is --O--, --NH-- or --NR3 -- and Z can be --NH-- or --NR3 --, and R3 is an alkyl of up to 6 carbons or a phenyl (preferred starting compounds for 29c) are 4-aminophenol or p-phenylenediamine), and

29d) 0 to 40 mol-% of repeating units of the formula

--O--R4 --O--

where R4 is a divalent radical consisting of at least one phenyl ring (a preferred starting compound is hydroquinone).

It is obvious that the repeating units can also be substituted by one or more alkyl or alkoxy of up to 4 carbons, halogen, phenyl or combinations thereof.

It is also possible in general for the thermotropically mesomorphic polymers to contain repeating units which allow branching points to be formed Examples of suitable starting compounds are 1,3,5-trihydroxybenzene, 3,5-dihydroxybenzoic acid or 5-hydroxyisophthalic acid. Polymers of this type are described, for example, in German Laid-Open Application DOS 3,346,549.

A block system is also possible for the polymers, in which case the polymer chains are composed of one or more blocks able to form mesomorphic melts and of one or more blocks of a thermoplast which is not thermotropically mesomorphic.

It is additionally possible to employ mixtures of various thermotropically mesomorphic polymers or blends of thermotropically mesomorphic polymers and other thermoplastic polymers or block copolymers composed of one or more blocks able to form a mesomorphic melt and of one or more blocks of a thermoplastic which is not thermotropically mesomorphic.

Processes for the preparation of the thermotropically mesomorphic polymers described above are conventional and are described in the literature, in particular in the individual patent applications mentioned with the products.

The implant materials according to the invention contain as component B) 5 to 70, preferably 10 to 65, and in particular 25 to 60, % by weight, based on the total weight, of an apatite.

Apatite is represented by the formula

Ca10 (PO4)6 (OH,F,Cl)2

and it is additionally possible for 1 to 10% by weight of carbonate ions (CO32-) to be present.

The preferred component B) is hydroxyapatite

Ca10 (PO4)6 (OH)2

which is commercially available. The apatite B) can contain a certain amount of whitlockite (Ca3 (PO4)2) without this having adverse effects.

The apatite can be produced by, for example, the processes described by Aoki et al. in Ceramics 10 (1975) 57-66.

If the apatite is employed in the form of spherical particles, these will have a diameter d50 (number average) of from 0.05 to 100 μm, preferably of from 0.1 to 50 μm.

Besides components A) and B), the implant materials according to the invention can contain as component C) up to 60, preferably 0.5 to 50, and in particular 2 to 40, % by weight of other fillers different from B).

It is obvious that in the case of physiologically objectionable or toxic fillers care must be taken that the filler does not come into contact with the organic tissue; biologically compatible fillers are generally preferred.

It is also possible to employ fibrous fillers as component C) to increase the rigidity further. Only metal fibers, carbon fibers and glass fibers of the various commercial types will be mentioned here. Others which can be used are inorganic fibers made from rock wool, zirconium oxide, mixed aluminum/silicon oxides, potassium titanate, barium titanate, silicon carbide and aluminum oxide. All these products are commercially available. Other possible fibrous fillers are to be found in EP-A 206,600.

Particular mention should also be made of glass fibers which have a substantial calcium phosphate content. Particularly suitable in this connection are glass fibers which have a total CaO and P2 O5 content of not less than 15% by weight, with the Ca/P molar ratio being in the range from 0.3:1 to 4.0:1, preferably from 0.8:1 to 2.0:1.

Also suitable are glass fibers coated with calcium phosphate compounds of this type.

Fibrous fillers of the two latter types, as well as processes for the preparation thereof, are described in DE-A 3,542,535.

The simplest way of producing the implant materials according to the invention is to mix the apatite B) and, where appropriate, the other fillers C) into a melt of the thermotropically mesomorphic polymer A). This can be carried out most simply in an extruder or an appropriate mixing device conventional for this purpose.

After the mixture has been produced it is possible to produce implant materials in almost any desired shape by injection molding, ie. the production is considerably simpler than with previously disclosed implants based on metals or ceramic materials, the shaping of which entails considerable expense.

The implant materials according to the invention are very compatible with the intact tissue in the immediate vicinity of the site of implantation and, at the same time, have great rigidity and strength. In particular, it is possible to adjust the rigidity of the implant to that of bone so that no substantial Young's modulus cracks take place at the interfaces and there is appropriate loading of the bone by the endoprosthesis. In addition, the implant materials according to the invention have great resistance to radiation, which means that they can be efficiently sterilized by γ rays. Moreover, as already mentioned, their production is particularly simple and low-cost.